Impact on Soybean Production and Value

Develop a more complete characterization of the HG types that occur in the major soybean producing areas in Nebraska to enable soybean growers to better select SCN resistant soybean varieties and rotate sources of resistance. This is important because most of the soybean varieties grown in the state, and across the United States, have SCN resistance coming from the line PI 88788. The findings of this study will promote the development of new sources of SCN resistance in the industry.

Loren Giesler (2013)

Key Terminology

Virulence is the ability of a pathogen to overcome an organism's defenses and cause disease.

HG (Heterodera glycines) Type refers to the sources of soybean cyst nematode (SCN) resistance that a particular SCN population can reproduce on. Each source of resistance has an HG type index number (Table 1) and populations of SCN are grown on soybean plants with each source to determine what sources they are capable of reproducing on. An example: an SCN population is capable of reproducing on PI88788, PI 209332 and PI 548316 (Cloud), so it has an HG Type 2.5.7.

Table 1. Sources of SCN resistance and the designated HG type index number

Study Objectives

The objectives of the project are to: 1) Establish the HG typing system for use in this survey and as a service for producers that encounter significant problems with SCN in Nebraska and 2) Determine the virulence phenotypes of Nebraska SCN populations.

Findings

An HG typing system was established for use in Nebraska and over 100 SCN populations were tested for HG type. HG types 2.5.7 are currently the predominant types identified (Table 2). Because most soybean varieties grown in Nebraska have PI 88788 resistance, it was important to determine the number of populations that are able to reproduce on this source of resistance. SCN populations that have been tested range greatly in their ability to reproduce PI 88788, but most had less than 30% the population that are capable of reproducing.

Next Steps

More surveys of soybean growing areas in Nebraska will be completed to continue characterizing the HG types found in the state. This will allow soybean growers to better select soybean varieties with appropriate resistance packages to prevent damage. The findings will be used to promote the development of new sources of resistance because the vast majority of soybean varieties grown have PI 88788 as the source of resistance.